George is right of course in all that he points out. But I think your question was about how to transfer over outlines rather than iCal tasks.
Currently you must work with an outliner (a good one at least on the Palm side) called ShadowPlan. It comes with Windows and Mac desktop versions also. This can sync over ShadowPlan outlines between the two versions.
For a while there was a set of Applescripts called OmniShadow which permitted Omni outlines to be synced over to the Palm Shadow app. It worked really well until Tiger when it died for me.
http://homepage.mac.com/james_sorenson/omnishadow.html
There must also be some way you can export an OOP file into Shadow desktop and then sync over to the Palm by hand.
But it's all became a bit klutzy for me once the simple link in OmniShadow was broken.
I tend to just export the file as RTF and then use my Docs To Go to sync it over. It doesn't function as an outline but I can at least read them.